Is there some way to retain circle and arc information in lines when they are exported? When I export circle and arc lines and then import them into other software they are all Polylines. This means I have to redraw circles and arcs as I can't create any dimensions other than distances.

Hi Val - which file format are you using and which other software are you bringing it into?

Circles and arcs are exported as smooth curves to 3DM, IGES, SAT, STEP, and AI formats.

The only format where MoI converts things into polylines itself is if you export to SKP format.

It is not possible to export smooth curves to SKP format since SketchUp does not itself have any method to represent smooth curves - SketchUp only handles polylines and not any kind of actual curved spline type objects.

So if you're exporting to SKP then that's just a fundamental limit of SketchUp.

If you're exporting to some other program using one of those other formats, then maybe the program that you are importing into is doing the polyline conversion itself, try to look for any import settings in that particular app to try and adjust that behavior.

I may not be using the proper terminology. I have tried exporting out as IGS SAT and used the converter 3dmcurves2dxf.
I tried importing them into turbocad 8 pro and doublecad (same software really) they export out and import fine but the information isn't retained that says it is a circle or an arc so when I try do do any dimension work it doesn't recognize the line as an arc or a circle. It just understands it as a polyline (spline) So I have to redraw all arcs and circles to be able to get any measurements. I have been poking around it the import setting but on the whole import settings are minimal.

I have been pampered by MOI as it is so easy to draw things up I hate to use other programs now.

Hi Val - re: terminology - usually a "polyline" means a series of line segments, so that's not a smooth curve unlike a "spline". It sounds like you don't mean that things are getting converted into just a set of angular lines like I had previously thought you meant.

So what happens in both of these cases for doing 3dmcurves2dxf as well as SAT format exports is that arcs and circles end up being translated as a general purpose NURBS spline curve which has the exact shape of a circle but it is apparently not recognized as a circle since it was not set up as an actual specialized "circle" type entity.

Some programs are able to analyze the shapes of NURBS spline curves that are imported and recognize them as circles and arcs but it seems like those programs are not doing that.

One thing you might try is to edit your moi.ini file and set:

[NURBS Export]
WriteAnalyticCurves=y

Then try exporting using IGES format after that - that should then make special arc and circle type entities in the IGES file instead of just general spline curve entities. And I guess if you've got your arcs joined with other curves into long connected pieces you will probably need to use Edit > Separate on them so that they are just individual pieces before they would get exported as an analytic.

I'm not sure if analytics works with SAT format or not - the translation library that I use for doing SAT export does not deal with analytic surfaces for SAT format (like spheres and cylinders), but I'm not sure if it does analytic curves or not. I think that analytic curves will work for IGES and STEP formats though.

But anyway try setting WriteAnalyticCurves=y and see if that helps any.

thanks but no such luck. The programs keep seeing them as splines which I can change to bezier which makes a mess of the line. Can you recommend a program (that doesn't cost an arm and a leg) that can recognize a nurbs curve as a circle? I had turbocad 8 pro from years ago and tried doublecad as it was free to hoping they had updated things. All I'm doing is 2D line work that I'm laying down the dimensions.

Hah, Changing the N to Y does work. for whatever reason the save wasn't kicking in, in notepad. I saved it but it would reverse back. I had closed out Moi before I opened the ini...... Anyway work like a charm. This time it seems like it took.